On various existing printed circuit boards, such as those having an array of electronic devices or components thereon, high frequency electrical interference or noise can be emitted. This noise can be detrimental to the circuitry on the printed circuit board because it can distort or interrupt a signal being transmitted. The circuits on the printed circuit boards are usually connected to external wiring harnesses via a header assembly.
One common type of header assembly comprises a connector body having a plurality of openings therethrough for receiving a plurality of pin terminals. The pin terminals have one end soldered to the individual circuits on the circuit board and the other end connectable to an external wiring harness.
To minimize the electrical noise from being emitted, it is common to house the circuit boards and the header assembly in a metal or aluminum box. However, these boxes have openings therein to allow the wiring harness to be connected to the header assembly and through which electrical noise can be emitted. An additional way to minimize the emission of electrical noise through the opening in the box is to metal plate the header assembly. However, even with these measures, electrical noise can still be transmitted through the metal pins extending from the printed circuit board to the external wiring harness. Electrical noise transmitted through the pins externally of the metal box can be transmitted throughout an automotive vehicle where it may cause disturbances in some of the circuitry of the vehicle.
To overcome electrical noise transmitted through the metal pins of a header assembly, it is common to provide a "pi" filter operatively associated with the metal pins of the header assembly. One common type of "pi" filter employs a combination of chip capacitors and a ferrite block. The ferrite block is connected to the metal pins intermediate their ends and serves as an inductor that is placed between chip capacitors which are individually soldered on the connector header on its side for connection with a wiring harness and another set of individual chip capacitors soldered on the circuit board to which the header connector is mounted or attached. This combination of capacitors and inductor creates a "pi" filter to reduce and eliminate any electrical noise being emitted through the metal pins.
A disadvantage of this type of filter is that it is costly due to the amount of precision soldering that is required. Each capacitor must be soldered to two metal pads on either the header or the printed circuit board. With the high number of circuits being used this creates a larger amount of soldering. To accomplish this, expensive high technology machinery is employed to solder the capacitors accurately on an assembly line basis in order to produce quality parts. In addition, the capacitors on the circuit board use valuable space on the printed circuit board. Without the capacitors present this space could be used for more circuitry or other electronic components.